verb (v)

• cause to run off the tracks(verb.motion)

  Example:
  They had planned to derail the trains that carried atomic waste.
  

  source: wordnet30
• run off or leave the rails(verb.motion)

  Example:
  The train derailed because a cow was standing on the tracks.
  

  Synonym:
  jump
  

  source: wordnet30
• To cause to run off from the rails of a railroad, as a locomotive.(verb)

  source: webster1913